1. Field of the Invention
The present invention relates to position measurement systems, exposure apparatuses, position measuring methods, exposure methods and device manufacturing methods, and tools and measuring methods, and more particularly, to a position measurement system which measures positional information of a movable body moving within a predetermined plane, an exposure apparatus comprising the system, a position measuring method in which positional information of a movable body moving within a predetermined plane is measured, an exposure method using the method and a device manufacturing method using the exposure method, and a tool which is preferable to measure positional relation of a head of an encoder and a mark detection system, and a measuring method using the tool.
2. Description of the Background Art
In a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
Now, because a semiconductor device or the like is formed by overlaying multilayer circuit patterns on a substrate (a wafer, a glass plate or the like), it is important that the overlay accuracy between each of the layers is good. Therefore, usually, a mark (an alignment mark) is installed in each of a plurality of shot areas on the substrate in advance, and positional information (a position coordinate) of the mark on a stage coordinate system of the exposure apparatus is detected. After the detection, based on the positional information of the mark and positional information already known of a pattern to be newly formed (for example, a reticle pattern), wafer alignment in which a shot area on the substrate is aligned to the pattern is performed. As a method of the wafer alignment, in consideration of throughput, global alignment such as Enhanced Global Alignment (EGA) whose details are disclosed in, for example, Kokai (Japanese Unexamined Patent Application Publication) No. 61-044429 bulletin and the like, has become mainstream.
Meanwhile, in the exposure apparatus, the position of a substrate stage which holds a substrate is usually measured using an interferometer; however, short-term fluctuation of the measurement values of the interferometer due to the temperature change on the beam path of the measurement beam of the interferometer is becoming unignorable. Therefore, there is a trend of using a linear encoder having less short-term fluctuation of the measurement values in comparison with the interferometer as the position measuring device of the substrate stage. However, in the case of measuring the position of a substrate stage that moves within a two-dimensional plane using a linear encoder, it is necessary to employ a placement of the encoder where the encoder does not interfere with the movement of the substrate stage and the beam path also becomes short. As a placement which satisfies such a condition, a placement where a plurality of heads is placed within a plane parallel to the two-dimensional plane along with a grating placed on the substrate stage can be considered. In this case, the position of the substrate stage has to be controlled while switching the plurality of heads, and furthermore, it is necessary to control the position of the substrate stage using the encoder based on the results of the wafer alignment so that the overlay accuracy becomes good. Accordingly, it becomes important to obtain the positional relation between a mark detection system which detects the alignment mark and each of the heads, and the positional relation of the plurality of heads (including the position information between the heads) with good precision.
Further, in order to perform position control of the substrate stage within the two-dimensional plane with good precision, for example, it is also important to control rotation of the substrate stage within the two-dimensional plane. However, in order to perform this rotation control with high accuracy, it is also necessary for reproducibility of the attitude of the substrate stage to be good at the time of reset.